The mild summer weather that prevailed in recent weeks has kept down heat-related mortality. Daily mortality is temperature-related. The relationship became apparent in the first series of hot summer days. A high temperature during the day frequently gives rise to a high mortality rate on the next day.
Daily mortality rate, 13 June-3 July 2005
First hot week claims 300 extra lives
In the week running from 20 to 26 June 2005 the first series of hot summer days was recorded with maximum temperatures reaching 25 º C and higher. The death toll in that particular week was 2, 800, some 300 above the level of an average week in early summer. The maximum daily temperature averaged 27.6 º C in that week. The mild summer weather prevailing in the following weeks, on the other hand, resulted in a relatively low mortality rate.
Weekly mortality rate, 16 June to 22 June 2005
The first weeks after the relatively hot week in June proved there is a straightforward relation between the number of daily deaths and the maximum daily temperature. Analysis of data covering the period 13 June to 3 July 2005 reveal that the daily mortality rate increases by 5 to 7 with each degree the maximum daily temperature rises. This also applies to other hot periods in the summers of the last five years.
Death rates respond promptly to high temperatures
Research demonstrates that temperature-related mortality is least affected by an average daily temperature of 16.5º C. The weekly number of deaths is indeed strongly temperature-related. Previous analyses conducted by Statistics Netherlands indicate that a temperature increase of one degree centigrade results in an additional 25 to 35 deaths a week. The average delay period was approximately three days. An analysis based on daily figures shows that the strongest effect on the daily mortality rate is recorded on the day immediately after a very hot summer day and that the high mortality rate is often retained during the next several days. A higher mortality rate is obviously linked to diseases of the respiratory and cardiovascular systems.
Joop Garssen and Carel Harmsen